The discovery of a Jupiter-mass planet orbiting
a star, Epsilon Eridani, a K2V star at a distance of only 3.22 pc,
was announced by an international team of astronomers led by Artie
Hatzes and William Cochran of the MacDonald Observatory. The
McDonald Observatory Press release is available here.

Geoff Marcy has recently been quoted as saying:
"We're now at a stage where we are finding planets faster than we
can investigate them and write up the results, "It's wonderful. Planet-hunting
has morphed from the marvelous to the mundane."

This discovery is far from mundane and is of special interest
to the CFHT community. The planet has an orbital period just under 7 years
and a semi-major axis of 3,3 AU. Hence the planet stands off
from the primary at an average angular distance of about 1 arc-second.
The orbital eccentricity appears to be 0.6 so that the separation
at apastron is as much as 1.6 arc-sec. This planet in Epsilon Eridani may
well be the first extra-solar planet to be directly imaged.

Epsilon Eridani was included among the sample of stars
studied by Bruce Campbell, Gordon Walker and Stevenson Yang for some 12
years, beginning in 1980, using the CFHT f/4 Coude spectrograph. This ground-breaking
program used a hydrogen fluoride absorption cell to provide a stable
reference system against which the very small Doppler shifts caused by
orbital motion could be precisely measured. This work was seminal
in that it demonstrated conclusively that radial velocity measurements
could be made to an accuracy sufficient to detect Jupiter-sized planetary
companions around the nearby stars. The results of this long survey are
discussed in Walker
et al 1995.

The Campbell-Walker survey was based on the premise that
extra-solar planetary systems were most likely to be similar to our own.
This kind of assumption is often made in the absence of any evidence to
the contrary. In our solar system, the gas giants are found at several
AU and have orbital periods of several years. As a consequence, the
CFHT survey was designed to measure the radial velocities of the program
stars at intervals of a few months over many years. After more than a decade
of painstaking effort the program was halted in 1992 without a conclusive
detection of a planetary system.

As so often happens in Astronomy, the discovery of the
first extra-solar planet by Michel Mayor and Didier Queloz in 1995
appeared to turn conventional wisdom on its head. They found that the planet
around 51 Pegasi was only 0.05 AU from its primary and the orbital
period was 4.2 days - vastly different from the expected yearly variations.
Among the 44 planets listed in the compilation here,
only 8 have periods exceeding a year.

However, planetary companions are far easier to detect
with the Doppler technique when they orbit close to their primary both
because the amplitude of the radial velocity variation is higher and because
conclusive observations can be made in a shorter period of time. As time
goes on, more distant planets with longer periods are increasingly likely
to be found.

The pioneering measurements made by the CFHT team were
used by the McDonald team and,indeed, uniquely provide the data that
defines the first of the observed orbital periods of the newly discovered
planet. The amplitude of the radial velocity curve is a mere 19 km/s.
The agreement between the CFHT data and the more recent data is remarkably
good.

On behalf of the CFHT, I extend congratulations to Bruce
Campbell, Gordon Walker and Stevenson Yang for their role in the
discovery of this new planet.